1. Field of the Invention
The invention relates to an electric motor vehicle, and in particular to an electric motor vehicle that detects an off state of a system main relay during a collision.
2. Description of Related Art
In recent years, electric motor vehicles, such as electric vehicles and hybrid vehicles, have widely been used. A method for driving a motor by stepping up voltage of DC power of a battery by a step-up converter and then converting the DC power to AC power for driving the motor by an inverter has widely been used in the electric motor vehicles. In order to stabilize the supplied DC power, a high-capacity smoothing capacitor is used for the step-up converter, the inverter, and the like. While the step-up converter and the inverter are in operation, electric charges that correspond to applied voltage are accumulated in this smoothing capacitor.
In such a case that the electric motor vehicle collides, the electric charges accumulated in the smoothing capacitor need to be immediately discharged. As a method for this, a method has been suggested in which, after a system main relay is turned off to cut off a connection between the battery and the smoothing capacitor, voltage of the smoothing capacitor is stepped up by a DC/DC converter and supplied to an auxiliary machine drive circuit, and the electric charges of the smoothing capacitor are discharged by driving an auxiliary machine when the electric motor vehicle collides (for example, see Japanese Patent Application. Publication No. 2011-10406 (JP 2011-10406 A) and Japanese Patent Application Publication No. 2010-178595 (JP 2010-178595 A)).